126 



GEOLOGY OF OHIO. 



The value of the fret glaze over one in which the ingredients are 

 merely mixed into a slip is very marked. The essential part of the glaze 

 is already a chemical compound. It is impossible for its components to 

 segregate out or to produce soft and hard spots on the glaze, if it has been 

 united once, all gases expelled and all chemical changes effected. When 

 applied on the ware and brought up to the melting point it quickly fuses 

 again, while the: freshly -compounded glaze has to make a chemical 

 combination out of a mechanical mixture in the same time. 



Glazes are colored to produce effects in the wares, by the use of 

 metallic oxides. Very little white ware is decorated in colors, under or 

 with the glaze. This class of work is mostly confined to ornamental pot- 

 tery. 



In burning the ware in the gloss kiln there is the danger of leaky 

 joints between the saggers or cracks by which the sulphurous gases from 

 the fire will get among the ware. 



. Any metallic oxides like lead or manganese are readily affected— the 

 results generally show a bluish white film or scum in the ware. 



An instance was observed of a piece of ware thus affected which 

 could be wiped bright by a piece of cloth, but after a few moments exposure 

 to the air the film would reappear. This phenomenon was probably due 

 to the presence of an inconceivably fine film of metallic lead, reduced to 

 this condition from the lead oxide of the glaze by contact with reducing 

 gases in the kiln. This film on being polished showed the bright metal- 

 lic surface of the lead, but it speedily became clouded again by the 

 oxydising action of the air. 



The decoration of the ware after it is finished is a separate branch 

 of the business. The colors used are enamel paints or readily fusible 

 glazes colored with metallic oxides and used as paints. The ornamenta- 

 tion is chiefly by "transfers" papers or "prints", though some finer ware 

 is decorated by hand painting. 



The development of the white ware business in Ohio sprung from 

 the manufacture of yellow wares at East . Liverpool, and the constant 

 improvement of these wares, by bringing on the better materials from 

 other states. The industry is most flourishing. The following table 

 shows the number and location of the manufactures. 



TABLE IV. 

 CC Ware Potteries 



The C. C. Thompson Co 



The D. E. McNicol Pottery Co . 



Cartright Bros 



Goodwin Bros 



Cartwright & Green 



George Scott & Sons 



Brockman Pottery Co 



Total . 



East Liverpool.'. 



Leetonia 

 Cincinnati, O. 



Total kilns 27 kilns 



8 kilns 



4 " 



5 ■' 

 8 " 



Total firms. 



